Reduction of the Lactose Content of Skim Milk by Continuous Countercurrent Cascade Ultrafiltration

Abstract

Lactose was continuously removed from skim milk using two ultrafilters in series, with intermediate recycle. Reduced recycle flow rates at constant lactose stream (permeate product) flow rate resulted in slightly better removal of lactose from the milk feed, although this mode of operation increased the protein loss from the final milk retentate product. Increased permeate flow rate at constant recycle rate removed more lactose from the feed but also resulted in more loss of protein. However, at its maximum, the loss of protein reprented only about 6% of the nutritional value of the milk. Under the experimental conditions studied, 58% of the lactose in the original skim milk could be continuously removed for the best combination of recycle and permeate flow rates. The experimental values of flow rates and compositions were reasonably well predicted by a mathematical model of the process.